Well, if it'd were to be a solid story,(if the woman is sincere) the fact of the mother and friends (bit gossip) having an opinion or prejudice wouldn't be a factor to consider, at all, sex worker or not (or sex performance actress) or whatever the job, is none of their business. IMO the main factors here to consider is that the whole adventure might have physical risks if the person is not cautious(and I was super ignorant of many things at 20, but...actually quite more than this guy, surely) also that he might get convinced to put a lot of money by being fooled (u never now on Internet, but he sounds like a good guy), somehow, (besides the trip costs, I mean), and there's a more than obvious emotional risk. This last one, if taken the punch the right way (and hoping not receiving physical punches from the ex), might be good to suffer it, might help learning to know people better, and stuff.
Edit: If she has not asked any money, that a good thing. Still doesn't means she's not going to...